Methods and apparatus to detect differences between images

ABSTRACT

Methods and apparatus to detect differences between images are disclosed. An example method to identify image differences disclosed herein comprises electronically determining whether a difference between a first block of pixels of a sample image and a second block of pixels of a reference image is resolvable using a transformation operation, when the difference between the first and second blocks is determined to be unresolvable, but not when the difference between the first and second blocks is determined to be resolvable, including the first block in an unresolved difference region of the sample image, and electronically generating a difference signature representative of the unresolved difference region, the difference signature to identify the unresolved difference region of the sample image.

FIELD OF THE DISCLOSURE

This disclosure relates generally to image processing and, moreparticularly, to methods and apparatus to detect differences betweenimages.

BACKGROUND

Print and other image-based advertisements often have more than oneversion, with each version corresponding to some minor modification of areference (e.g., parent) advertisement. For example, a particular familyof print advertisements can be based on a reference (e.g., parent)advertisement displaying a common background image and commoninformation (e.g., for the product/service being advertised), but witheach particular version also displaying version specific information(e.g., logos, prices, addresses, phone numbers, dates, etc.,corresponding to a particular market, advertising campaign, etc.)overlaid on the background image. Video advertisements (e.g.,commercials) can similarly have more than one version. Advertisers areoften interested in not only detecting occurrences of theirprint/image/video advertisements, but also determining which version ofthe advertisement was detected. Many conventional advertisement versiondetection techniques are entirely manual and involve an analyst visuallycomparing a sample image representative of a detected advertisement toeach possible version of the advertisement. Other conventionaltechniques utilize pixel-wise comparison techniques to highlight pixelsin the sample image that differ from the reference advertisement,thereby allowing the analyst to focus his/her attention on only thehighlighted regions to identify which version of the advertisement wasdetected. However, in practice, a common background used for a family ofadvertisements may be slightly altered (intentionally orunintentionally) during post-production of a particular version of theadvertisement. Such alterations can cause existing pixel-wise comparisontechniques to be prone to false highlighting or over highlighting of thesample images being analyzed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of an example image difference identificationsystem capable of identifying differences between images according tothe example techniques described herein.

FIG. 2 illustrates example sample and reference images to be processedby the image difference identification system of FIG. 1.

FIG. 3 is a block diagram of an example difference resolver to resolvedifferences between images that may be used to implement the imagedifference identification system of FIG. 1.

FIG. 4 illustrates example sample, reference and difference images to beprocessed by the difference resolver of FIG. 3.

FIG. 5 is block diagram of an example image difference recognizercapable of recognizing differences between images according to theexample techniques described herein.

FIG. 6 is a flowchart representative of example machine readableinstructions that may be executed to perform a difference identificationprocess to implement the image difference identification system of FIG.1.

FIG. 7 is a flowchart representative of example machine readableinstructions that may be used to implement the example machine readableinstructions of FIG. 6 and/or executed to perform a differenceresolution process to implement the difference resolver of FIG. 3 and/orthe image difference identification system of FIG. 1.

FIG. 8 is a flowchart representative of example machine readableinstructions that may be used to implement the example machine readableinstructions of FIG. 7 and/or executed to perform a block resolutionprocess to implement the difference resolver of FIG. 3 and/or the imagedifference identification system of FIG. 1.

FIG. 9 is a flowchart representative of example machine readableinstructions that may be executed to perform a difference recognitionprocess to implement the image difference recognizer of FIG. 5.

FIG. 10 is a block diagram of an example processing system that mayexecute the example machine readable instructions of any, some or all ofFIGS. 6-9 to implement the image difference identification system ofFIG. 1, the difference resolver of FIG. 3 and/or the image differencerecognizer of FIG. 5.

DETAILED DESCRIPTION

Methods and apparatus to detect differences between images are disclosedherein. Although the following discloses example methods and apparatusincluding, among other components, software executed on hardware, itshould be noted that such methods and apparatus are merely illustrativeand should not be considered as limiting. For example, it iscontemplated that any or all of these hardware and software componentscould be implemented exclusively in hardware, exclusively in software,exclusively in firmware, or in any combination of hardware, software,and/or firmware. Accordingly, while the following describes examplemethods and apparatus, persons having ordinary skill in the art willreadily appreciate that the examples provided are not the only way toimplement such methods and apparatus.

The example techniques to detect differences between images describedherein include example techniques to identify differences between imagesand example techniques to recognize differences between images.Generally, the purpose of difference identification is to determine thedifferent versions of a reference advertisement, determine the imageregions that differ between advertisements and determine descriptiveinformation to represent and categorize the different advertisementversions. In contrast, the purpose of difference recognition isgenerally to recognize a sample image as corresponding to an alreadyidentified and categorized (e.g., via difference identification) versionof a reference advertisement. As described in greater detail below, manyof the example techniques described herein utilize elastic block-wise(also referred to as patch-wise) image comparison, along with furthertransformation techniques, to detect and highlight differences betweenimages to enable advertisement version identification. These exampletechniques also generate information representative of the detected andhighlighted differences to enable automated recognition of a detectedadvertisement as corresponding to a particular version.

In an example technique to identify image differences described herein,an example image signature matcher compares a sample image signaturerepresentative of a sample image (e.g., corresponding to anadvertisement being identified) and a plurality of reference imagesignatures representative of a respective plurality of reference images(e.g., corresponding to different possible advertisements and/oradvertisement versions) to select a reference image similar to thesample image (e.g., corresponding to an advertisement at least in thesame family as the advertisement being identified). Then, an exampledifference resolver determines whether a difference between a firstblock of pixels of the sample image and a second block of pixels of theselected reference image is resolvable using a transformation operation.Examples of such transformation operations include, but are not limitedto, shift operations, intensity adjustments, color adjustments, etc. Inthis example, when the difference between the first and second blocks isdetermined to be unresolvable, but not when the difference between thefirst and second blocks is determined to be resolvable, the differenceresolver includes the first block in an unresolved difference region ofthe sample image. In this way, blocks that are resolvable using atransformation operation can be ignored as being caused by, for example,post-production alterations, minor distortion during transmission and/orstorage, etc., whereas blocks that are not resolvable likely correspondto an actual content difference between advertisement versions. In atleast some examples, the unresolvable blocks are presented to a humananalyst for confirmation. Then, after all blocks of the sample image areprocessed, an example difference signature generator generates adifference signature representative of the unresolved (e.g., andconfirmed) difference region, with the difference signature to be usedto represent and identify the unresolved (e.g., and confirmed)difference region of the sample image. For example, the unresolved(e.g., and confirmed) difference region corresponds to aversion-specific region of the advertisement being identified, and thedifference signature is stored for use in recognizing thisversion-specific region in later difference recognition processing.

In an example technique to recognize image differences described herein,an example image signature generator generates a sample image signaturerepresentative of a sample image (e.g., representative of a detectedadvertisement). Then, an example image signature matcher obtains areference image (e.g., corresponding to a reference, or parent, versionof the detected advertisement) associated with a reference imagesignature determined to substantially match the sample image signature.Next, a difference signature generator generates a difference signaturerepresentative of a first region of the sample image correspondingspatially with (e.g., having the same size, shape and location as) areference difference region associated with a first version (e.g., ofpotentially a family of different versions) of the reference image(e.g., as determined by prior difference identification processing).Then, a difference signature matcher compares the generated differencesignature and a reference difference signature representative of thereference difference region (e.g., as determined by prior differenceidentification processing) to determine whether the sample imagecorresponds to the first version of the reference image (e.g., and,therefore, the detected advertisement corresponds to the first versionof the reference advertisement).

At least some of the example techniques to detect differences betweenimages described herein provide substantial benefits over conventionaltechniques. For example, as mentioned above, many conventionaladvertisement version detection techniques are entirely manual andinvolve an analyst visually comparing a sample image representative of adetected advertisement to each possible version of the advertisement.Unlike such manual techniques, advertisement version detection performedusing the example image difference detection techniques described hereinis substantially automated with, for example, unresolved differenceregion(s) of a sample image being identified and highlightedautomatically for analyst evaluation. Furthermore, unlike conventionalpixel-wise comparison techniques that are prone to false highlighting orover highlighting of the sample images being analyzed, the example imagedifference detection techniques described herein utilize elasticblock-wise (also referred to as patch-wise) image comparison thataccounts for and is blind to (e.g., and thus can discard or ignore)differences resulting from post-production alterations and/or other suchtransformation operations and, instead, focuses on differences likely tobe actual changes in content between advertisement versions, therebyyielding more robust and accurate difference identification andhighlighting, at least under some operating scenarios.

Turning to the figures, a block diagram of an example image differenceidentification system 100 capable of identifying differences betweenimages according to the example techniques described herein isillustrated in FIG. 1. The image difference identification system 100 ofFIG. 1 includes an example image difference identifier 105 to comparesample images with reference images stored in, for example, a storageunit 110 to determine whether the sample image corresponds to a versionof one or more of the reference images and, if so, to identify one ormore version-specific difference regions in the sample image. In anexample implementation, the sample image is representative of a detectedadvertisement undergoing analysis, and the reference images stored inthe storage unit 110 represent reference advertisements, each of whichmay have multiple versions as described above. The storage unit 110 maybe implemented by any type of a storage or memory device, a database,etc., such as the mass storage device 1030 and/or the volatile memory1018 included in the example processing system 1000 of FIG. 10, which isdescribed in greater detail below.

In the illustrated example of FIG. 1, the image difference identifier105 includes an example image sampler 115 to obtain the sample imagerepresentative of, for example, a detected advertisement undergoinganalysis. The image sampler 115 can be implemented by any image samplingtechnology or combination of technologies compatible with the mediaformat(s) of the advertisements to be processed. For example, in thecase of print advertisements, the image sampler 115 can be implementedby a scanner, camera or any other optical sensor capable of generatingan electronic image representative of a print advertisement. As anotherexample, in the case video advertisements, the image sampler 115 can beimplemented by a video processor, frame grabber, camera or any otheroptical sensor capable of generating an image frame of the videoadvertisement.

The image difference identifier 105 employs image signatures toautomatically identify one or more reference images stored in thestorage unit 110 that are substantially similar to the sample imageobtained by the image sampler 115. Generally, an image signature is aproxy representative of the associated image, and can take the form of,for example, one or more digital values, a waveform, a thumbnail image,etc. Because image signatures are proxies representing their associatedimages, the signatures of two images can be compared to determinewhether their respective images are substantially similar or identical.Generally, if two image signatures substantially match (e.g., at leastwithin some tolerance or deviation level), then the respective imagesthey represent are substantially similar or identical. Typically,signature comparison is simpler and requires less processing resourcesthan direct image comparison. In the illustrated example, the imagedifference identifier 105 employs image signatures in which two imagesthat are substantially similar except for one or more difference regions(e.g., corresponding to different versions of an advertisement) willusually have substantially matching signatures (e.g., at least withinsome tolerance level). Examples of types of image signatures capable ofbeing employed by the image difference identifier include, but are notlimited to, the examples described in U.S. Patent Publication No.2008/0068622, entitled “Methods and Apparatus to Identify Images inPrint Advertisements” and published on Mar. 20, 2008, U.S. PublicationNo. 2006/0153296, entitled “Digital Video Signature Apparatus andMethods for Use with Video Program Identification Systems” and publishedon Jul. 13, 2006, U.S. Pat. No. 6,633,651, entitled “Method andApparatus for Recognizing Video Sequences” and issued on Oct. 14, 2003,and U.S. Pat. No. 6,577,346, entitled “Recognizing a Pattern in a VideoSegment to Identify the Video Segment” and issued on Jun. 10, 2003. U.S.Patent Publication Nos. 2008/0068622 and 2006/0153296, and U.S. Pat.Nos. 6,633,651 and 6,577,346, are hereby incorporated by reference intheir respective entireties.

To determine a sample image signature representative of the sample imageobtained by the image sample 115, the image difference identifier 105includes an example image signature generator 120. The image signaturegenerator 120 generates the sample image signature using any appropriatesignature generation technique, such as the example techniques describedin U.S. Patent Publication Nos. 2008/0068622 and 2006/0153296, and U.S.Pat. Nos. 6,633,651 and 6,577,346, mentioned above. The sample imagesignature generated by the image signature generator 120 is provided toan example image signature matcher 125. The image signature matcher 125compares the sample image signature to one or more reference imagesignatures stored in the storage unit 110 and representative of arespective one or more reference images also stored in the storage unit110. The image signature matcher 125 can implement various comparisoncriteria, such as a cross-correlation value, a Hamming distance, etc.,to determine whether two signatures match or substantially match withina particular tolerance level (e.g., which may be predetermined,specified as a configuration parameter or input, etc.).

If the image signature matcher 125 determines that the sample imagesignature does not match any reference image signature in the storageunit 110, an example image database manager 130 included in the imagedifference identifier 105 instructs or otherwise causes the imagesampler 115 to store the sample image in the storage unit 110 for use asa new reference image corresponding to a new reference advertisement.The image database manager 130 also causes the sample image to bedisplayed on an example user configuration terminal 135 to allow ananalyst to analyze the sample image. Furthermore, the analyst isprompted to enter descriptive information via the terminal 135 tocharacterize the new reference advertisement to be associated with thedisplayed sample image. The descriptive information is then stored withthe sample image in the storage unit 110. Further description of theuser interface terminal 135 is provided below.

If, however, the image signature matcher 125 determines that the sampleimage signature substantially matches a reference image signature in thestorage unit 110, the image signature matcher 125 provides the sampleimage and the selected matching reference image to an example differenceresolver 140 included in the image difference identifier 105. Forillustrative purposes, an example sample image 205 and an examplereference image 210 that could be determined by the image signaturematcher 125 to substantially match are illustrated in FIG. 2. The sampleimage 205 and the reference image 210 correspond to different versionsof the same advertisement. In particular, both images include a commonbackground image region 215 and a common text region 220 having contentthat is unchanged between the different versions of the advertisement,although these regions may undergo post-production alteration (e.g.,such as the illustrated rotation of the regions 215 and 220 in thesample image 205 relative to the reference image 210). However, theimages also include version-specific regions containing informationand/or other content specific to the particular version of theadvertisement represented by each image. For example, the referenceimage 210 includes a first version-specific region 225 containing priceand contact information specific to a first version of theadvertisement. Similarly, the sample image 205 includes a secondversion-specific region 230 containing price and contact informationspecific to a second version of the advertisement. As such, although theimage signature matcher 125 can determine that the sample image 205 andthe reference image 210 substantially match (e.g., due to substantiallymatching image signatures resulting from the prevalence of the commonregions 215 and 220), each image also contains version-specific regions(e.g., the regions 225 and 230) corresponding to the different versionsof the advertisement represented by the sample image 205 and thereference image 210.

Returning to FIG. 1, and with reference to FIG. 2, the differenceresolver 140 determines whether there are any regions of difference(e.g., such as the regions 225 and 230) between the sample image and thereference image determined by the image signature matcher 125 tosubstantially match (e.g., such as the images 205 and 210). Such regionsof difference, also referred to herein as difference regions, cancorrespond to regions of version-specific information that vary amongdifferent versions of a reference, or parent, advertisement. However,difference regions can also result from one or more image transformationoperations being performed intentionally or unintentionally duringstorage, transmission, reception, etc., of the image or videoadvertisement. In the illustrated example, the difference resolver 140implements elastic block-wise (also referred to as patch-wise) imagecomparison to resolve difference regions resulting from post-productionalterations of other such image transformation operations. As such, thedifference resolver 140 can account for and discard or ignore resolvabledifference regions caused by such post-production alterations and/orimage transformation operations and, instead, focus identification onany unresolvable difference region(s) in the sample image likely tocorrespond to actual differences between advertisement versionsrepresented by the respective sample and reference images. An exampleimplementation of the difference resolver 140 is illustrated in FIG. 3and described in greater detail below.

Assuming the difference resolver 140 identifies an unresolved differenceregion in the sample image, an example difference classifier 145included in the image difference identifier 105 obtains classificationinformation to identify, for example, the advertisement versioncorresponding to the unresolved difference region. To obtain suchclassification information, the difference classifier 145 of theillustrated example causes the sample image to be displayed on the userconfiguration terminal 135 with the unresolved difference region beinghighlighted (e.g., by varying the intensity and/or color of the sampleimage in the unresolved difference region). Additionally, in at leastsome example implementations, the difference classifier 145 causes theselected matching reference image to also be displayed on the userconfiguration terminal 135 with a region of the reference imagecorresponding spatially with the unresolved difference region of thesample image also being highlighted (e.g., to allow efficient,side-by-side comparison of these regions of the two images). In at leastsome examples, an analyst can activate a zooming/expanding feature tocause only a portion of the sample image and the matching referenceimage at the same location (e.g., the location of the unresolveddifference region) to be displayed (e.g., with or without highlighting).Furthermore, the analyst is prompted to enter classification informationvia the terminal 135 to characterize the advertisement versioncorresponding to the highlighted, unresolved difference region of thesample image. The entered classification information is provided to thedifference classifier 145 for storage in the storage unit 110.Additionally, the analyst can indicate that a particular highlightedregion is insignificant and, thus, can be ignored. This indication andassociated descriptive information of the highlighted region can bestored in the storage unit 110 such that, when a similar differenceregion is encountered again, it can be ignored as being insignificant.The user configuration terminal 135 can be implemented by, for example,a computer terminal, a computer workstation, a laptop/notebook, apersonal digital assistant (PDA), a mobile phone, etc., or any othertype of user input device.

In the illustrated example, the image difference identifier 105 alsoincludes an example difference signature generator 150 to generate adifference signature for each unresolved difference region of the sampleimage identified by the difference resolver 140. Similar to an imagesignature generated by the image signature generator 120, a differencesignature generated by the difference signature generator 150 isgenerated from characteristics of the unresolved difference region andis a proxy (e.g., such as one or more digital values, a waveform, athumbnail image, etc.) representative of the unresolved differenceregion. Alternatively, the difference signature generated by thedifference signature generator 150 for an unresolved difference regioncould be a copy of the some or all of the unresolved difference regionitself (e.g., such as when the unresolved difference region isrelatively small). Generally, the difference signatures generated by thedifference signature generator 150 are larger (e.g., more descriptive)than the image signatures generated by the image signature generator 120to ensure that the difference signature is a unique proxy representativeof its associated difference region (e.g., to reduce false detection ofadvertisement versions that could result when different differenceregions corresponding to different advertisement versions arerepresented by the same or substantially similar difference signatures).In an example implementation, the difference signature generated by thedifference signature generator 150 is a small image (e.g., such as acopy of some or all of the associated difference region itself, or athumbnail or other lower resolution image) representative of theunresolved difference region. Other example techniques that may be usedby the difference signature generator 150 to generate differencesignatures include, but are not limited to, the examples described inU.S. Patent Publication Nos. 2008/0068622 and 2006/0153296, and U.S.Pat. Nos. 6,633,651 and 6,577,346, mentioned above.

The classification information obtained by the difference classifier 145and the difference signature generated by the difference signaturegenerator 150 for an unresolved difference region of the sample imageidentified by the difference resolver 140 are provided to the imagedatabase manager 130 for storage in the storage unit 110. In an exampleimplementation, the image database manager 130 appends theclassification information, the difference signature and differenceregion location information as a new entry in a record maintained forthe matching reference image. The image database manager 130 alsoannotates the new entry to indicate that the new entry corresponds to aparticular version, as identified in the classification information, ofthe reference advertisement corresponding to the reference image. Thestored classification information, difference signature and differenceregion location information can then be used during subsequent imagedifference recognition processing, as described in greater detail below.

While an example manner of implementing the image difference identifier105 has been illustrated in FIG. 1, one or more of the elements,processes and/or devices illustrated in FIG. 1 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example storage unit 110, the example image sampler 115,the example image signature generator 120, the example image signaturematcher 125, the example image database manager 130, the exampledifference resolver 140, the example difference classifier 145, theexample difference signature generator 150 and/or, more generally, theexample image difference identifier 105 of FIG. 1 may be implemented byhardware, software, firmware and/or any combination of hardware,software and/or firmware. Thus, for example, any of the example storageunit 110, the example image sampler 115, the example image signaturegenerator 120, the example image signature matcher 125, the exampleimage database manager 130, the example difference resolver 140, theexample difference classifier 145, the example difference signaturegenerator 150 and/or, more generally, the example image differenceidentifier 105 could be implemented by one or more circuit(s),programmable processor(s), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)), etc. When any of the appendedclaims are read to cover a purely software and/or firmwareimplementation, at least one of the example image difference identifier105, the example storage unit 110, the example image sampler 115, theexample image signature generator 120, the example image signaturematcher 125, the example image database manager 130, the exampledifference resolver 140, the example difference classifier 145 and/orthe example difference signature generator 150 are hereby expresslydefined to include a tangible medium such as a memory, digital versatiledisk (DVD), compact disk (CD), etc., storing such software and/orfirmware. Further still, the example image difference identifier 105 ofFIG. 1 may include one or more elements, processes and/or devices inaddition to, or instead of, those illustrated in FIG. 1, and/or mayinclude more than one of any or all of the illustrated elements,processes and devices.

A block diagram of an example implementation of the difference resolver140 of FIG. 1 is illustrated in FIG. 3. The difference resolver 140 ofFIG. 3 includes an example image scaler 305 to scale a sample imageobtained via the image sampler 115 to coincide with the size of amatching reference image selected by the image signature matcher 125.Additionally or alternatively, the image scaler 305 can perform anyother image registration operation (e.g., such as rotation, deskewing,cropping, etc.) to cause the sample image to coincide with the matchingreference image in terms of size, shape, spatial orientation, etc.

The difference resolver 140 of FIG. 3 also includes an exampledifference image determiner 310 to determine a difference image based onthe sample image and the reference image. In an example implementation,the difference image determiner 310 determines a pixel-wise differenceimage by computing the difference (e.g., in terms of luminance, colormap, etc.) between respective pixels of the sample image and thereference image. For illustrative purposes, an example difference image405 that could be determined by the difference image determiner 310based on an example sample image 410 (e.g., such as the sample image205) and an example reference image 415 (e.g., such as the referenceimage 210) is illustrated in FIG. 4. In the example of FIG. 4, eachpixel 420 of the difference image 405 is determined by computing thedifference between respective pixels 425 and 430 of the sample image 410and the reference image 415.

In at least some examples supporting video processing, multiplereferences images may be used to represent a particular video segment(e.g., containing a reference advertisement of interest), with thereference images taken at different intervals of the segment. In suchexamples, rather than creating and processing difference imagescorresponding to each reference image of the video segment, thedifference image determiner 310 may instead: (1) obtain a single sampleimage representative of the entire video segment, (2) compare the sampleimage to each of the multiple reference images for the video segment,and then (3) output a single difference image corresponding to thesample image and reference image comparison yielding the smallest (e.g.,minimum) difference.

Returning to FIG. 3, the illustrated example difference resolver 140further includes an example difference image segmenter 315 to partitionthe difference image determined by the difference image determiner 310into blocks (also referred to as patches) each containing multiplepixels. For example, with reference to FIG. 4, the difference imagesegmenter 315 could partition the difference image 405 into multipleblocks 435 each containing multiple pixels 420. In an exampleimplementation, the size of each block 435 into which the differenceimage 405 is partitioned is predetermined, specified as a configurationinput or otherwise set based on a size of the image differences expectedto be encountered in an unresolved difference region being processed bythe difference resolver 140. For example, if the expected differencescorrespond to different phone numbers, prices, etc., corresponding todifference advertisement versions, the size and shape of each block 435could be set to be some fractional or multiple of the size of acharacter in the character set used for the phone numbers, prices, etc.,in the advertisement.

Returning to FIG. 3, the segmented difference image is provided to anexample block resolver 320 included in the difference resolver 140. Theblock resolver 320 determines whether any of the blocks of the segmenteddifference image indicate a significant difference (also referred to asa substantial difference) between the sample image and the referenceimage and, if so, whether such a difference is resolvable as beingcaused by post-production alterations or other such transformationoperations and, thus, is not associated with an actual advertisementversion difference. For example, a significant (or substantial)difference between two images may correspond to an actual difference inimage content (e.g., such as the two images containing different imageobjects at a particular location), whereas an insignificant (orinsubstantial) difference that can be ignored may correspond to minorcolor and/or intensity variations or other minordiscrepancies/distortion between the two images. As noted above, adifference (e.g., a significant or substantial difference) is consideredresolvable if, for example, one or more transformation operations couldbe performed on either or both of the images being compared to eliminate(or substantially eliminate within some tolerance or deviation level)this difference between the two images. To perform its processing, theblock resolver 320 includes an example block difference evaluator 325 todetermine a difference metric (e.g., such as a sum of pixel values in ablock of the difference image) for each block in the segmenteddifference image. In an example implementation, the block differenceevaluator 325 compares a block's difference metric with a threshold. Ifthe threshold is not exceeded, thereby indicating no significantdifference between the sample and reference images at that block'slocation, the block difference evaluator 325 discontinues processing ofthat block. However, if the threshold is exceeded, thereby indicating asignificant difference between the sample and reference images at thatblock's location, the block difference evaluator 325 forms a sampleblock from the sample image corresponding spatially with the block ofthe difference image, as well as a reference block from the referenceimage also corresponding spatially with the block of the differenceimage. For example, with reference to FIG. 4, if the block differenceevaluator 325 were to determine that the distance metric associated witha block 440 of the difference image 405 exceeds the threshold, the blockdifference evaluator 325 would form a sample block 445 from the sampleimage 410 and a reference block 450 from the reference image 415 bothcorresponding spatially with the block 440 of the difference image 405.

Returning to FIG. 3, if the block difference evaluator 325 forms asample block from the sample image and a reference block from thereference image because the associated block in the difference image hasa difference metric indicating a significant difference between theseblocks, the block difference evaluator 325 provides the sample block ofthe sample image and the reference block of the reference image to anexample block flatness evaluator 330 included in the block resolver 320.The block flatness evaluator 330 determines whether the differencebetween the sample block of the sample image and the reference block ofthe reference image is resolvable using a transformation operationcorresponding to, for example, an intensity adjustment or a coloradjustment. For example, the block flatness evaluator 330 determineswhether the sample block of the sample image is flat or, in other words,whether the sample block includes pixels exhibiting a substantiallysimilar first color and first intensity. Similarly, the block flatnessevaluator 330 determines whether the reference block of the referenceimage is flat or, in other words, whether the reference block includespixels exhibiting a substantially similar second color and secondintensity. The second color and/or intensity may be similar to ordifferent from the first color and/or intensity. If both the sampleblock and the reference block are determined to be flat, the blockflatness evaluator 330 determines that the difference between the sampleblock and the reference block can be resolved by transforming the sampleimage using either or both of an intensity or color adjustment (e.g.,either globally or locally at the location of the sample block). In thiscase, the difference was likely caused by post-production alteration,such as use of a different paper color, different gray levels, differentcolor levels, etc., for a particular print advertisement, differentgains for a video advertisement, etc., and/or other intensity/colorchanges occurring during storage, transmission, reception, etc., of theadvertisement corresponding to the sample image and is not indicative ofa different advertisement version.

However, if the block flatness evaluator 330 determines that either orboth of the sample block and the reference block are not flat, anexample block neighborhood evaluator 335 included in the block resolver320 is invoked. The block neighborhood evaluator 335 determines whetherthe difference between the sample block of the sample image and thereference block of the reference image is resolvable using atransformation operation corresponding to shift operation. For example,with reference to FIG. 4, the block neighborhood evaluator 335determines whether the sample block (e.g., block 445) of the sampleimage substantially matches any block of pixels of the reference imagein a neighborhood of blocks adjacent to the reference block (e.g., block450). If the sample block is determined to match a block in theneighborhood of the reference block, the block neighborhood evaluator335 determines that the difference between the sample block and thereference block can be resolved by transforming the sample image byshifting the image (e.g., either globally or locally at the location ofthe sample block) and, thus, the difference was likely caused bypost-production alteration and/or during storage, transmission,reception, etc., of the advertisement corresponding to the sample imageand is not indicative of a different advertisement version.

If the block resolver 320 does not determine a transformation operationcapable of resolving the difference between the sample block of thesample image and the reference block of the reference image, the blockresolver 320 indicates that the difference is unresolvable. The blockresolver 320 also invokes an example unresolved region grouper 340included in the difference resolver 140 of FIG. 3 to include theunresolved sample block in an unresolved difference region of the sampleimage. After all blocks of the difference image are processed, theunresolved region grouper 340 outputs any unresolved differenceregion(s) of the sample image for subsequent processing by, for example,the difference classifier 145 and the difference signature generator150.

While an example manner of implementing the difference resolver 140 ofFIG. 1 has been illustrated in FIG. 3, one or more of the elements,processes and/or devices illustrated in FIG. 3 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example image scaler 305, the example difference imagedeterminer 310, the example difference image segmenter 315, the exampleblock resolver 320, the example block difference evaluator 325, theexample block flatness evaluator 330, the example block neighborhoodevaluator 335, the example unresolved region grouper 340 and/or, moregenerally, the example difference resolver 140 of FIG. 3 may beimplemented by hardware, software, firmware and/or any combination ofhardware, software and/or firmware. Thus, for example, any of theexample image scaler 305, the example difference image determiner 310,the example difference image segmenter 315, the example block resolver320, the example block difference evaluator 325, the example blockflatness evaluator 330, the example block neighborhood evaluator 335,the example unresolved region grouper 340 and/or, more generally, theexample difference resolver 140 could be implemented by one or morecircuit(s), programmable processor(s), ASIC(s), PLD(s) and/or FPLD(s),etc. When any of the appended claims are read to cover a purely softwareand/or firmware implementation, at least one of the example differenceresolver 140, the example image scaler 305, the example difference imagedeterminer 310, the example difference image segmenter 315, the exampleblock resolver 320, the example block difference evaluator 325, theexample block flatness evaluator 330, the example block neighborhoodevaluator 335 and/or the example unresolved region grouper 340 arehereby expressly defined to include a tangible medium such as a memory,DVD, CD, etc., storing such software and/or firmware. Further still, theexample difference resolver 140 of FIG. 3 may include one or moreelements, processes and/or devices in addition to, or instead of, thoseillustrated in FIG. 3, and/or may include more than one of any or all ofthe illustrated elements, processes and devices.

A block diagram of an example image difference recognizer 500 capable ofrecognizing differences between images according to the exampletechniques described herein is illustrated in FIG. 5. The imagedifference recognizer 500 includes an example image sampler 515 toobtain a sample image representative of, for example, a detectedadvertisement undergoing analysis. For example, the image sampler 515can be the same as, or implemented substantially similar to, the imagesampler 115 of FIG. 1. The image difference recognizer 500 of FIG. 5also includes an example image signature generator 520 to generate asample image signature representative of the sample image obtained bythe image sampler 515. For example, the image signature generator 520can be the same as, or implemented substantially similar to, the imagesignature generator 120 of FIG. 1

The image difference recognizer 500 of FIG. 5 further includes anexample image signature matcher 525 to compare the sample imagesignature generated by the image signature generator 520 to one or morereference image signatures stored in an example storage unit 510 andrepresentative of a respective one or more reference images also storedin the storage unit 510. The reference images stored in the storage unit510 correspond to respective reference advertisements and theirassociated different versions. The storage unit 510 can be the same as,or implemented substantially similar to, the storage unit 110 of FIG. 1,and the image signature matcher 525 can be the same as, or implementedsubstantially similar to, the image signature matcher 125 of FIG. 1. Inthe case of video advertisements, the image signature matcher 525 canalso implement scene change detection to potentially reduce processingto one sample image and corresponding signature for a detected scene(e.g., instead of processing each sample image determined by the imagesampler 515 and corresponding signature generated by the image signaturegenerator 520). In such an example, the image signature matcher 525stores a scene signature corresponding to a sample image representing apreviously detected scene and for which reference image signaturecomparison has already been performed. For each subsequent imagesignature generated for each subsequent sample image (e.g., sampleframe) of the video being analyzed, the image signature matcher 525compares the new image signature with the stored scene signature. If thenew image signature fails to match the stored scene signature (e.g.,indicating a scene change), or the video ends, the new image signatureis determined to be a new scene signature corresponding to a new sceneand, thus, the image signature matcher 525 compares this new scenesignature to the one or more reference image signatures as describedabove. In at least some example, the sample image corresponding to thisnew scene signature is also stored by the image signature matcher 525 asa key image representative of this new detected scene.

If the image signature matcher 525 determines that the sample image(e.g., scene) signature does not match any reference image signature inthe storage unit 510, an example reporting unit 530 included in theimage difference recognizer 500 generates a reporting record, entry,etc., or other reporting information to indicate that the sample image(e.g., or the images contained in the scene) does not correspond to anyrecognized version of any recognized advertisement corresponding to thereference image(s) stored in the storage unit 510. However, if the imagesignature matcher 525 determines that the sample image (e.g., scene)signature does match a reference image signature in the storage unit510, the image signature matcher 525 selects the matching referenceimage from the storage unit 510. As noted above, each reference image isassociated with one or more different versions of a referenceadvertisement. Each different version of the reference image issubstantially similar except for one or more version-specific differenceregions uniquely associated with each version of the reference image.For each reference image, the storage unit 510 stores version specificinformation, such as the version-specific difference regions associatedwith each version, as well as a difference signature representative ofeach difference region (e.g., as determined and generated by the imagedifference identification system 100 of FIG. 1) and other classificationinformation. Accordingly, the image signature matcher 525 also invokesan example difference signature generator 550 to generate a differencesignature representative of each region of the sample imagecorresponding spatially to a respective version-specific differenceregion classified as being associated with a particular version of theselected matching reference image (e.g., based on the classificationinformation stored in the storage unit 510). In other words, thedifference signature generator 550 generates a respective differencesignature for each difference region or set of regions of the sampleimage specified by the stored classification information ascorresponding to a different version of the matching reference image.The difference signature generator 550 can be the same as, orimplemented substantially similar to, the difference signature generator150 of FIG. 1.

The image difference recognizer 500 of FIG. 5 includes an exampledifference signature matcher 555 to compare the difference signature(s)generated by the difference signature generator 550 for the specifieddifference region(s) of the sample image with the respective referencedifference signature(s) representative of the respectiveversion-specific difference region(s) of the reference image todetermine whether the sample image corresponds to a particular versionof the reference image. If the generated difference signature(s) for thesample image and the respective reference difference signature(s) for aparticular version of the reference image match, then the reporting unit530 generates a reporting record, entry, etc., or other reportinginformation. Such generated reporting information indicates, forexample, that the sample image corresponds to the particular version ofthe reference advertisement indicated by the classification informationin the storage unit 510 as being associated with the matching referencedifference signatures and respective difference regions. As such, bycomparing reference signatures for version-specific reference imagedifference regions with corresponding difference signatures for the sameregions of the sample image, the image difference recognizer 500automatically recognizes whether the sample image corresponds to aparticular version of an advertisement corresponding to the referenceimage.

While an example manner of implementing the image difference recognizer500 has been illustrated in FIG. 5, one or more of the elements,processes and/or devices illustrated in FIG. 5 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example storage unit 510, the example image sampler 515,the example image signature generator 520, the example image signaturematcher 525, the example reporting unit 530, the example differencesignature generator 550, the example difference signature matcher 555and/or, more generally, the example image difference recognizer 500 ofFIG. 5 may be implemented by hardware, software, firmware and/or anycombination of hardware, software and/or firmware. Thus, for example,any of the example storage unit 510, the example image sampler 515, theexample image signature generator 520, the example image signaturematcher 525, the example reporting unit 530, the example differencesignature generator 550, the example difference signature matcher 555and/or, more generally, the example image difference recognizer 500could be implemented by one or more circuit(s), programmableprocessor(s), ASIC(s), PLD(s) and/or FPLD(s), etc. When any of theappended claims are read to cover a purely software and/or firmwareimplementation, at least one of the example image difference recognizer500, the example storage unit 510, the example image sampler 515, theexample image signature generator 520, the example image signaturematcher 525, the example reporting unit 530, the example differencesignature generator 550 and/or the example difference signature matcher555 are hereby expressly defined to include a tangible medium such as amemory, DVD, CD, etc., storing such software and/or firmware. Furtherstill, the example image difference recognizer 500 of FIG. 5 may includeone or more elements, processes and/or devices in addition to, orinstead of, those illustrated in FIG. 5, and/or may include more thanone of any or all of the illustrated elements, processes and devices.

Flowcharts representative of example machine readable instructions thatmay be executed to implement and, some or all of the image differenceidentification system 100, the image difference identifier 105, thestorage unit 110, the image sampler 115, the image signature generator120, the image signature matcher 125, the image database manager 130,the difference resolver 140, the difference classifier 145, thedifference signature generator 150, the image scaler 305, the differenceimage determiner 310, the difference image segmenter 315, the exampleblock resolver 320, the block difference evaluator 325, the blockflatness evaluator 330, the block neighborhood evaluator 335, theunresolved region grouper 340, the difference recognizer 500, thestorage unit 510, the image sampler 515, the image signature generator520, the image signature matcher 525, the reporting unit 530, thedifference signature generator 550 and/or the difference signaturematcher 555 are shown in FIGS. 6-9. In these examples, the machinereadable instructions represented by each flowchart may comprise one ormore programs for execution by: (a) a processor, such as the processor1012 shown in the example processing system 1000 discussed below inconnection with FIG. 10, (b) a controller, and/or (c) any other suitabledevice. The one or more programs may be embodied in software stored on atangible medium such as, for example, a flash memory, a CD-ROM, a floppydisk, a hard drive, a DVD, or a memory associated with the processor1012, but the entire program or programs and/or portions thereof couldalternatively be executed by a device other than the processor 1012and/or embodied in firmware or dedicated hardware (e.g., implemented byan application specific integrated circuit (ASIC), a programmable logicdevice (PLD), a field programmable logic device (FPLD), discrete logic,etc.).

For example, any or all of the image difference identification system100, the image difference identifier 105, the storage unit 110, theimage sampler 115, the image signature generator 120, the imagesignature matcher 125, the image database manager 130, the differenceresolver 140, the difference classifier 145, the difference signaturegenerator 150, the image scaler 305, the difference image determiner310, the difference image segmenter 315, the example block resolver 320,the block difference evaluator 325, the block flatness evaluator 330,the block neighborhood evaluator 335, the unresolved region grouper 340,the difference recognizer 500, the storage unit 510, the image sampler515, the image signature generator 520, the image signature matcher 525,the reporting unit 530, the difference signature generator 550 and/orthe difference signature matcher 555 could be implemented by anycombination of software, hardware, and/or firmware. Also, one or more ofthe machine readable instructions represented by the flowcharts of FIGS.6-9 may be implemented manually. Further, although the example machinereadable instructions are described with reference to the flowchartsillustrated in FIGS. 6-9, many other techniques for implementing theexample methods and apparatus described herein may alternatively beused. For example, with reference to the flowcharts illustrated in FIGS.6-9, the order of execution of the blocks may be changed, and/or some ofthe blocks described may be changed, eliminated, combined and/orsubdivided into multiple blocks.

Example machine readable instructions 600 that may be executed toperform a difference identification process to implement the imagedifference identifier 105 and, more generally, the image differenceidentification system 100 of FIG. 1 are illustrated in FIG. 6. Theexample machine readable instructions 600 may be executed atpredetermined intervals, based on an occurrence of a predetermined event(e.g., such as obtaining or detecting a sample image corresponding to anadvertisement to be identified), as a background process, etc., or anycombination thereof. With reference to FIG. 1, the machine readableinstructions 600 of FIG. 6 begin execution at block 605 at which theimage sampler 115 included in the image difference identifier 105samples or otherwise obtains a sample image representative of, forexample, a detected advertisement undergoing version identification. Atblock 610, the image signature generator 120 included in the imagedifference identifier 105 generates a sample image signaturerepresentative of the sample image, as described above. Then, at block615 the image signature matcher 125 included in the image differenceidentifier 105 compares the sample image signature generated at block610 with one or more reference image signatures representative of arespective one or more reference images corresponding to respectivereference advertisements. The reference image signatures and referenceimages are stored in a storage unit 110, as described above.

If the sample image signature does not match any reference imagesignature (block 615), then at block 620 the sample image is stored inthe storage unit 110 for use as a new reference image corresponding to apotentially new reference advertisement. Descriptive information forclassifying this new reference image is also obtained at block 620, forexample, after the new reference image is confirmed by an analyst tocorrespond to a new reference advertisement. Additionally oralternatively, at block 620 the detection of an unmatched sample imagecan be reported, which could cause further analysis of the sample imageto be performed (e.g., to determine whether the unmatched sample imageis representative of a new advertisement). Execution of the machinereadable instructions 600 then ends.

However, if the sample image signature does match (or substantiallymatches) a reference image signature (block 615), the image signaturematcher 125 selects the matching reference image. At block 625, thedifference resolver 140 included in the image difference identifier 105determines whether any difference regions between the sample image andthe reference image are not resolvable using one or more transformationoperations and, thus, likely correspond to actual differences betweenadvertisement versions represented by the respective sample andreference images. Example machine readable instructions that may be usedto perform the difference resolution processing at block 625 areillustrated in FIG. 7 and described in greater detail below.

If there are no unresolved difference regions identified by thedifference resolution processing at block 625 (or, in other words, anydifference regions are resolvable using one or more transformationoperations), then at block 630 the sample image is determined tocorrespond to the reference advertisement represented by the matchingreference image (because any differences between the sample andreference images were likely the result of post-production alterationsand/or other such transformation operations). Therefore, execution ofthe example machine readable instructions 600 ends.

If, however, one or more unresolved regions are identified by thedifference resolution processing (block 630), then at block 635 thedifference classifier 145 included in the image difference identifier105 prompts a user to classify the unresolved difference region(s) ofthe sample image by, for example, identifying a version of the referenceadvertisement to which the unresolved difference region(s) correspond,and/or by identifying one or more of the unresolved difference regionsas representing insignificant differences that can be ignored. At block640, the difference signature generator 150 included in the imagedifference identifier 105 generates difference signature(s)representative of the unresolved difference region(s). As discussedabove, a difference signature generated at block 640 is typicallydifferent from the image signature generated at block 610. For example,the difference signature generated at block 640 is typically generatedusing only the respective unresolved difference region of the sampleimage, whereas the image signature generated at block 610 is typicallygenerated using the entire sample image. Also, the difference signaturegenerated at block 640 is typically larger than the image signaturegenerated at block 610. For example, a difference signature generated atblock 640 could be a copy of some or all of the associated unresolveddifference region itself, a thumbnail image or a proxy value that islonger (e.g., has more digits or bits) than the image signaturegenerated at block 610.

Then, at block 645 the image database manager 130 stores theclassification information, difference region location information andrespective difference signature(s) in the storage unit 110 as a newversion of the reference advertisement corresponding to the matchingreference image. Execution of the example machine readable instructions600 then ends.

Example machine readable instructions 625 that may be used to implementthe difference resolution processing at block 625 of FIG. 6 and/or thedifference resolver 140 included in the image difference identifier 105of FIG. 1 are illustrated in FIG. 7. With reference to the exampleimplementation of the difference resolver 140 illustrated in FIG. 3,execution of the machine readable instructions 625 of FIG. 7 begins atblock 705 at which the image scaler 305 included in the differenceresolver 140 scales and/or performs any other registration operation(s)to cause the sample image to coincide with the matching reference image(or sequence of matching reference images in the case of video segmentprocessing) in terms of size, shape, spatial orientation, etc. Then, atblock 710 the difference image determiner 310 included in the differenceresolver 140 determines a pixel-wise difference image by computing thedifference between respective pixels of the sample image and thereference image. Alternatively, in the case of video segment processing,at block 710 the difference image determiner 310 can compare the sampleimage to each of the multiple reference images for the video segment,and then output a single difference image corresponding to the sampleimage and reference image comparison yielding the smallest (e.g.,minimum) difference. Next, at block 715 the difference image segmenter315 included in the difference resolver 140 partitions the differenceimage determined at block 710 into blocks (also referred to as patches)each containing multiple pixels, with the size of each block being basedon the size of the image differences expected to be encountered whencomparing different versions of an advertisement.

At block 720, the block resolver 320 included in the difference resolver140 determines whether any of the blocks of the segmented differenceimage indicate a difference between the sample image and the referenceimage and, if so, whether the difference is resolvable as being causedby post-production alteration and/or one or more other suchtransformation operations and, thus, is not associated with an actualadvertisement version difference. Example machine readable instructionsthat may be used to perform the block resolution processing at block 720are illustrated in FIG. 8 and described in greater detail below.

After completion of the block resolution processing at block 720, atblock 725 the unresolved region grouper 340 included in the differenceresolver 140 groups any unresolved blocks into unresolved differenceregions of the sample image. As discussed above, these unresolveddifference regions can be highlighted to focus analysis on only thoseregions of the sample image that are likely to be specific to aparticular version of the reference advertisement corresponding to thematching reference image. Execution of the example machine readableinstructions 625 then ends.

Example machine readable instructions 720 that may be used to implementthe block resolution processing at block 720 of FIG. 7 and/or the blockresolver 320 included in the difference resolver 140 of FIG. 3 areillustrated in FIG. 8. With reference to the example implementation ofthe block resolver 320 illustrated in FIG. 3, execution of the machinereadable instructions 720 of FIG. 8 begins at block 805 at which theblock resolver 320 obtains the blocks of the segmented difference imagedetermined from the sample image and the matching reference image. Then,for each block in the difference image (block 810), the block differenceevaluator 325 included in the block resolver 320 determines a differencemetric corresponding to a sum of the pixel values in the block of thedifference image being processed (block 815). Then, at block 820 theblock difference evaluator 325 compares the block's difference metricwith a threshold (e.g., which may be predetermined, specified as aconfiguration parameter, or otherwise set). If the threshold is notexceeded (block 820), thereby indicating no significant differencebetween the sample and reference images at that block's location, thenat block 825 the block resolver 320 marks the block of the sample imagecorresponding spatially with the block of the difference image beingprocessed as being resolved.

However, if the threshold is exceeded (block 820), thereby indicating asignificant difference between the sample and reference images at thatblock's location, then at block 830 the block difference evaluator 325forms a sample block (P) from the sample image corresponding spatiallywith the block of the difference image, and forms a reference block (P′)from the reference image also corresponding spatially with the block ofthe difference image. Next, at block 825 the block flatness evaluator330 included in the block resolver 320 determines whether both thesample block (P) from the sample image and the corresponding referenceblock (P′) from the reference image are flat, which would indicate thatthe difference between the sample block (P) of the sample image and thereference block (P′) of the reference image is resolvable using atransformation operation corresponding to, for example, an intensityadjustment or a color adjustment. If both the sample block (P) and thecorresponding reference block (P′) are flat (block 835), then at block825 the block resolver 320 marks the sample block (P) as being resolved.

However, if at least one of the sample block (P) and the correspondingreference block (P′) are not flat (block 835), then at block 840 theblock flatness evaluator 330 determines whether both the sample block(P) and the corresponding reference block (P′) are not flat. If one ofthe sample block (P) and the corresponding reference block (P′) is flatand the other is not flat (block 840), then at block 845 the blockresolver 320 marks the sample block (P) as being unresolved. If,however, both the sample block (P) and the corresponding reference block(P′) are not flat (block 840), then at block 850 the block neighborhoodevaluator 335 included in the block resolver 320 determines whether thesample block (P) of the sample image matches any block in theneighborhood of blocks adjacent to the reference block (P′) of thereference image, which would indicate that the difference between thesample block (P) and the reference block (P′) is resolvable using atransformation operation corresponding to a shift operation. Forexample, at block 850 the block neighborhood evaluator 335 can compute acorrelation value (e.g., based on a pixel-wise difference) between eachneighbor block adjacent to the reference block (P′) and the sample block(P) and then compare the correlation value to a threshold to determinewhether the sample block (P) substantially matches any neighbor blockadjacent to the reference block (P′). If a matching neighbor block isfound (block 855), then at block 825 the block resolver 320 marks thesample block (P) as being resolved. However, if a matching neighborblock is not found (block 855), then at block 845 the block resolver 320marks the sample block (P) as being unresolved.

After all blocks of the difference image have been processed (block860), execution of the example machine readable instructions 720 ends.In at least some example implementations, execution of the examplemachine readable instructions 720 is repeated to perform blockresolution processing with the roles of the sample image and thereference image being reversed. The set of all unresolved blocks thenbecomes the union of unresolved blocks determined during each iterationof the block resolution processing.

Example machine readable instructions 900 that may be executed toperform a difference recognition process to implement the imagedifference recognizer 500 of FIG. 5 are illustrated in FIG. 9. Theexample machine readable instructions 900 may be executed atpredetermined intervals, based on an occurrence of a predetermined event(e.g., such as the obtaining or detection of a sample imagecorresponding to an advertisement to be recognized), as a backgroundprocess, etc., or any combination thereof. With reference to FIG. 5, themachine readable instructions 900 of FIG. 9 begin execution at block 905at which the image sampler 515 included in the image differencerecognizer 500 samples or otherwise obtains a sample imagerepresentative of, for example, a detected advertisement undergoingversion recognition. At block 910, the image signature generator 520included in the image difference recognizer 500 generates a sample imagesignature representative of the sample image, as described above. Then,at block 915 the image signature matcher 525 included in the imagedifference recognizer 500 compares the sample image signature generatedat block 910 with one or more reference image signatures representativeof a respective one or more reference images corresponding to respectivereference advertisements. In the case of video advertisements, at block915 the image signature matcher 525 may employ scene change detection,as described above, to reduce processing to one scene signature for eachdetected scene (e.g., instead of processing the signatures for each ofthe individual images included in a detected scene). The reference imagesignatures and reference images are stored in a storage unit 510, asdescribed above.

If the sample image (e.g., or scene) signature does not match anyreference image signature (block 915), then at block 920 the reportingunit 530 included in the image difference recognizer 500 indicates thatthe sample image does not (e.g., or the sample images included in thedetected scene do not) correspond to any recognized version of anyrecognized advertisement corresponding to the reference image(s) storedin the storage unit 510. Execution of the machine readable instructions900 then ends. However, if the sample image (e.g., or scene) signaturedoes match a reference image signature (block 915), the image signaturematcher 525 selects the matching reference image from the storage unit510. Then, at block 925 the difference signature generator 550 includedin the image difference recognizer 500 generates a difference signaturerepresentative of each region of the sample image (e.g., or key imagerepresentative of the detected scene) corresponding spatially to arespective version-specific difference region associated with aparticular version of the selected matching reference image (e.g., asspecified by classification information in the storage unit 510).

Next, at block 930 the difference signature matcher 555 included in theimage difference recognizer 500 compares the difference signature(s)generated at block 925 for the sample image (e.g., or key image) withthe respective reference difference signature(s) stored in the storageunit 510 for the selected matching reference image. If no match is found(block 930), then at block 935 the reporting unit 530 indicates that thesample image does not correspond to any recognized version of therecognized advertisement corresponding to selected matching referenceimage. Execution of the machine readable instructions 900 then ends.However, if the difference signature(s) generated for the sample imagematch the respective reference difference signature(s) for a particularversion of the selected matching reference image, then at block 940 thereporting unit 530 indicates that the sample image corresponds to theparticular version of the reference advertisement indicated by theclassification information in the storage unit 510 as being associatedwith the matching reference difference signatures and respectivedifference regions. Execution of the machine readable instructions 900then ends.

FIG. 10 is a block diagram of an example processing system 1000 capableof implementing the apparatus and methods disclosed herein. Theprocessing system 1000 can be, for example, a server, a personalcomputer, a personal digital assistant (PDA), an Internet appliance, orany other type of computing device.

The system 1000 of the instant example includes a processor 1012 such asa general purpose programmable processor. The processor 1012 includes alocal memory 1014, and executes coded instructions 1016 present in thelocal memory 1014 and/or in another memory device. The processor 1012may execute, among other things, the machine readable instructionsrepresented in FIGS. 6-9. The processor 1012 may be any type ofprocessing unit, such as one or more microprocessors from the Intel®Centrino® family of microprocessors, the Intel® Pentium® family ofmicroprocessors, the Intel® Itanium® family of microprocessors, and/orthe Intel XScale® family of processors. Of course, other processors fromother families are also appropriate.

The processor 1012 is in communication with a main memory including avolatile memory 1018 and a non-volatile memory 1020 via a bus 1022. Thevolatile memory 1018 may be implemented by Static Random Access Memory(SRAM), Synchronous Dynamic Random Access Memory (SDRAM), Dynamic RandomAccess Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/orany other type of random access memory device. The non-volatile memory1020 may be implemented by flash memory and/or any other desired type ofmemory device. Access to the main memory 1018, 1020 is typicallycontrolled by a memory controller (not shown).

The processing system 1000 also includes an interface circuit 1024. Theinterface circuit 1024 may be implemented by any type of interfacestandard, such as an Ethernet interface, a universal serial bus (USB),and/or a third generation input/output (3GIO) interface.

One or more input devices 1026 are connected to the interface circuit1024. The input device(s) 1026 permit a user to enter data and commandsinto the processor 1012. The input device(s) can be implemented by, forexample, a keyboard, a mouse, a touchscreen, a track-pad, a trackball,an isopoint and/or a voice recognition system.

One or more output devices 1028 are also connected to the interfacecircuit 1024. The output devices 1028 can be implemented, for example,by display devices (e.g., a liquid crystal display, a cathode ray tubedisplay (CRT)), by a printer and/or by speakers. The interface circuit1024, thus, typically includes a graphics driver card.

The interface circuit 1024 also includes a communication device such asa modem or network interface card to facilitate exchange of data withexternal computers via a network (e.g., an Ethernet connection, adigital subscriber line (DSL), a telephone line, coaxial cable, acellular telephone system, etc.).

The processing system 1000 also includes one or more mass storagedevices 1030 for storing software and data. Examples of such massstorage devices 1030 include floppy disk drives, hard drive disks,compact disk drives and digital versatile disk (DVD) drives. The massstorage device 1030 may implement the storage unit 110 and/or thestorage unit 510. Alternatively, the volatile memory 1018 may implementthe storage unit 110 and/or the storage unit 510.

As an alternative to implementing the methods and/or apparatus describedherein in a system such as the processing system of FIG. 10, the methodsand or apparatus described herein may be embedded in a structure such asa processor and/or an ASIC (application specific integrated circuit).

Finally, although certain example methods, apparatus and articles ofmanufacture have been described herein, the scope of coverage of thispatent is not limited thereto. On the contrary, this patent covers allmethods, apparatus and articles of manufacture fairly falling within thescope of the appended claims either literally or under the doctrine ofequivalents.

1. A method to identify image differences, the method comprising:electronically determining whether a difference between a first block ofpixels of a sample image and a second block of pixels of a referenceimage is resolvable using a transformation operation; when thedifference between the first and second blocks is determined to beunresolvable, but not when the difference between the first and secondblocks is determined to be resolvable, including the first block in anunresolved difference region of the sample image; and electronicallygenerating a difference signature representative of the unresolveddifference region, the difference signature to identify the unresolveddifference region of the sample image.
 2. A method as defined in claim 1wherein the transformation operation is a shift operation, and furthercomprising determining whether the first block of the sample imagesubstantially matches a third block of pixels of the reference image ina neighborhood of the second block to determine whether the differencebetween the first block of the sample image and the second block of thereference image is resolvable.
 3. A method as defined in claim 2 whereinthe neighborhood of the second block comprises blocks of pixels of thereference image adjacent to the second block, and wherein the firstblock of the sample image substantially matches the third block of thereference image when a correlation value is less than or equals athreshold.
 4. A method as defined in claim 2 further comprisingdetermining that the difference between the first and second blocks isresolvable when the first block of the sample image is determined tomatch any block in the neighborhood of the second block of the referenceimage.
 5. A method as defined in claim 1 wherein the transformationoperation is at least one of an intensity or color adjustment, andfurther comprising determining whether the first block is substantiallyflat and whether the second block is substantially flat to determinewhether the difference between the first block of the sample image andthe second block of the reference image is resolvable.
 6. A method asdefined in claim 5 wherein the first block is substantially flat whenthe first block includes pixels exhibiting a substantially similar firstcolor and first intensity, and wherein the second block is substantiallyflat when the second block includes pixels exhibiting a substantiallysimilar second color and second intensity.
 7. A method as defined inclaim 5 further comprising determining that the difference between thefirst and second blocks is resolvable when both the first and secondblocks are determined to be substantially flat.
 8. A method as definedin claim 1 further comprising: determining a difference image based onthe sample image and the reference image; partitioning the differenceimage into a plurality of blocks of pixels; determining that acorrelation value for a third block of the difference image exceeds athreshold; forming the first block of the sample image to correspondspatially with the third block of the difference image; and forming thesecond block of the reference image to correspond spatially with thethird block of the difference image.
 9. (canceled)
 10. (canceled)
 11. Amethod as defined in claim 1 wherein the reference image is a firstreference image, and further comprising: generating a sample imagesignature representative of the sample image, the sample image signaturebeing different from the difference signature representative of theunresolved difference region; comparing the sample image signature and aplurality of reference image signatures representative of a respectiveplurality of reference images; and selecting the first reference imagefrom the plurality of reference images when a first reference imagesignature representative of the first reference image is determined tosubstantially match the sample image signature.
 12. (canceled)
 13. Amethod as defined in claim 1 further comprising obtaining informationdescribing the unresolved difference region in response to generating auser prompt including the sample image with the unresolved differenceregion being highlighted.
 14. A tangible article of manufacture storingmachine readable instructions which, when executed, cause a machine to:determine whether a difference between a first block of pixels of asample image and a second block of pixels of a reference image isresolvable using a transformation operation; when the difference betweenthe first and second blocks is determined to be unresolvable, but notwhen the difference between the first and second blocks is determined tobe resolvable, include the first block in an unresolved differenceregion of the sample image; and generate a difference signaturerepresentative of the unresolved difference region, the differencesignature to identify the unresolved difference region of the sampleimage.
 15. A tangible article of manufacture as defined in claim 14wherein the transformation operation is a shift operation, and whereinthe machine readable instructions, when executed, further cause themachine to determine whether the first block of the sample imagesubstantially matches a third block of pixels of the reference image ina neighborhood of adjacent blocks of the second block to determinewhether the difference between the first block of the sample image andthe second block of the reference image is resolvable.
 16. A tangiblearticle of manufacture as defined in claim 14 wherein the transformationoperation is at least one of an intensity or color adjustment, andwherein the machine readable instructions, when executed, further causethe machine to determine whether the first block is substantially flatand whether the second block is substantially flat to determine whetherthe difference between the first block of the sample image and thesecond block of the reference image is resolvable, the first block beingsubstantially flat when the first block includes pixels exhibiting asubstantially similar first color and first intensity, and the secondblock being substantially flat when the second block includes pixelsexhibiting a substantially similar second color and second intensity.17. A tangible article of manufacture as defined in claim 14 wherein themachine readable instructions, when executed, further cause the machineto: determine a difference image based on the sample image and thereference image; partition the difference image into a plurality ofblocks of pixels; determine that a correlation value for a third blockof the difference image exceeds a threshold; form the first block of thesample image to correspond spatially with the third block of thedifference image; and form the second block of the reference image tocorrespond spatially with the third block of the difference image.
 18. Atangible article of manufacture as defined in claim 14 wherein thereference image is a first reference image, and wherein the machinereadable instructions, when executed, further cause the machine to:generate a sample image signature representative of the sample image,the sample image signature being different from the difference signaturerepresentative of the unresolved difference region, the differencesignature being larger than the sample image signature; compare thesample image signature and a plurality of reference image signaturesrepresentative of a respective plurality of reference images; and selectthe first reference image from the plurality of reference images when afirst reference image signature representative of the first referenceimage is determined to substantially match the sample image signature.19. (canceled)
 20. (canceled)
 21. An image difference identifiercomprising: an image signature matcher to compare a sample imagesignature representative of a sample image and a plurality of referenceimage signatures representative of a respective plurality of referenceimages to select a reference image similar to the sample image; adifference resolver to: determine whether a difference between a firstblock of pixels of the sample image and a second block of pixels of thereference image is resolvable using a transformation operation; andinclude the first block in an unresolved difference region of the sampleimage when the difference between the first and second blocks isdetermined to be unresolvable, but not when the difference between thefirst and second blocks is determined to be resolvable; and a differencesignature generator to generate a difference signature representative ofthe unresolved difference region, the difference signature beingdifferent from the sample image signature, the difference signature toidentify the unresolved difference region of the sample image.
 22. Animage difference identifier as defined in claim 21 wherein thetransformation operation is a shift operation, and wherein thedifference resolver is to determine whether the first block of thesample image substantially matches a third block of pixels of thereference image in a neighborhood comprising adjacent blocks of thesecond block to determine whether the difference between the first blockof the sample image and the second block of the reference image isresolvable.
 23. An image difference identifier as defined in claim 21wherein the transformation operation is at least one of an intensity orcolor adjustment, and wherein the difference resolver is to determinewhether the first block is substantially flat and whether the secondblock is substantially flat to determine whether the difference betweenthe first block of the sample image and the second block of thereference image is resolvable, the first block being substantially flatwhen the first block includes pixels exhibiting a substantially similarfirst color and first intensity, and the second block beingsubstantially flat when the second block includes pixels exhibiting asubstantially similar second color and second intensity.
 24. An imagedifference identifier as defined in claim 21 further comprising: adifference image determiner to determine a difference image based on thesample image and the reference image; a difference image segmenter topartition the difference image into a plurality of blocks of pixels; anda block resolver to: determine that a correlation value for a thirdblock of the difference image exceeds a threshold; form the first blockof the sample image to correspond spatially with the third block of thedifference image; and form the second block of the reference image tocorrespond spatially with the third block of the difference image. 25.An image difference identifier as defined in claim 21 wherein thedifference signature is larger than the sample image signature andcomprises at least one of an image representative of the unresolveddifference region, or one or more proxy values representative of theunresolved difference region 26-45. (canceled)